The present invention relates to an insulation system for aircraft fuselages and, in particular, to an insulation system for increasing the burn through resistance of aircraft fuselages to provide passengers with additional time within which to evacuate an airplane in the event of an external fuel fire.
Currently, the Federal Aviation Administration (the FAA) is testing various aircraft fuselage sidewall constructions to determine if they can demonstrate a significant increase in burn through resistance in a simulated exterior fire condition. For example, the test simulates a situation where the aircraft is on the ground and a jet fuel fire ignites next to the outside of the fuselage.
The baseline fuselage sidewall construction in current use combines an interior trim panel with one or more layers of Microlite AA fiberglass insulation blanket, encapsulated in a reinforced Mylar film, that is positioned in the framework of an aircraft with an exterior aluminum skin. The fiberglass blanket currently used in the baseline construction is 0.42 pound per cubic foot (pcf).times.1 inch (6.7 Kg/m.sup.3.times.25.4 mm) or 0.6 pcf.times.1 inch (9.6 Kg/m.sup.3.times.25.4 mm) Microlite AA. In some constructions used by aircraft manufacturers, one or all of the Microlite AA fiberglass blanket layers are replaced with a 0.3 pcf.times.1 inch to a 0.6 pcf.times.1 inch (4.8 Kg/m.sup.3.times.25.4 mm to 9.6 Kg/m.sup.3.times.25.4 mm) polyimide foam.
In a real or simulated fire condition, all of the individual fuselage components melt away quickly and permit flame to penetrate into the passenger compartment The baseline fuselage construction typically provides only a couple of minutes of burn through protection in these tests. There are many ways to improve burn through protection in an aircraft fuselage. However, the most obvious solutions require a significant addition of weight which is undesirable in aircraft construction.